Objectives

This study tested the hypothesis, first proposed by Chaussinand, that individual-level immunity acquired from exposure to tuberculosis may have contributed to the disappearance of leprosy from western Europe.

Methods

The epidemiological consequences of cross-immunity were assessed by the formulation of a mathematical model of the transmission dynamics of tuberculosis and leptosy.

Resuits.

The conditions under which Mvcobacterium tuberculosis could have eradicated Mycobacterium teprae were derived in terms of he basic reproductive rates of the two infections and the degree of cross-immunity.

Conclusions

If the degree of cross-immunity between two diseases within an individual is known, then the epidemiological consequences of this cross-immunity can be assessed with transmission modeling The results of this analysis, in combination with previous estimates of the basic reproductive rate of tuberculosis and degree of cross-immunity, imply that tuberculosis could have contributed to the decline of leptosy if the basic reproductive rate of leprosy was low.